KR102563118B1 - Convection Optimization for Mixed Feature Electroplating - Google Patents

Abstract

Various embodiments herein relate to methods and apparatus for electroplating material onto substrates. The substrate is usually a semiconductor substrate. The various techniques described herein utilize multiple different electroplating stages, and convection conditions vary between the different electroplating stages. In many cases, at least one ultra-low convection stage is used. An ultra-low convection stage may be paired with a first stage and a final stage with higher convection conditions. By controlling convection conditions as described herein, highly uniform plating results can be achieved even when differently sized and/or differently shaped features are provided on a single substrate.

Description

Convection Optimization for Mixed Feature Electroplating

Cross reference to related applications

This application claims priority to and the benefit of U.S. Patent Application Serial No. 15/785,251, filed on October 16, 2017, entitled "CONVECTION OPTIMIZATION FOR MIXED FEATURE ELECTROPLATING", which is hereby incorporated by reference in its entirety for all purposes. The specification is incorporated by reference.

In integrated circuit (IC) fabrication, a conductive material, such as copper, is often deposited by electroplating onto a conductive seed layer to fill one or more recessed features on a wafer substrate. Electroplating is the method of choice for depositing metal into the vias and trenches of a wafer during damascene processing, and is also used in through-silicon TSVs (TSVs), which are fairly large vertical electrical connections used in 3D ICs and 3D packages. used to fill vias. Electroplating may also be used to fill through resist wafer-level packaging (WLP) structures.

During electroplating, electrical contacts are made to the seed layer (typically at the periphery of the wafer), and the wafer is electrically biased to act as a cathode. The wafer is brought into contact with an electroplating solution, which contains ions of the metal to be plated and often contains additives that may promote certain filling behavior. Electroplating is typically performed for an amount of time sufficient to fill the recessed features with metal. Unwanted metal deposited on the field region of the wafer is then removed by a planarization operation, such as chemical mechanical polishing (CMP).

Various techniques described herein relate to methods, apparatus, and systems for electroplating a material onto a substrate. Typically, at least one ultra-low convection stage is provided. This ultra low convection stage may be paired with either a medium convection stage or a high convection stage. A medium convection stage or a high convection stage may be provided at the start of the electroplating process and/or at the end of the electroplating process. In various embodiments, the substrate includes features of at least two different sizes (eg, features having different critical dimensions (CDs) and/or depths). The ultra-low convection stage targets a targeted relative deposition rate in differently sized features, e.g., to fill features in a uniform manner, or to target a specific gap height between features after they have been filled. can be used to Previously, and particularly in certain embodiments as discussed further below, controlling deposition rates relative to differently shaped/sized features has become difficult or impossible.

In one aspect of the disclosed embodiments, a method of electroplating a material on a substrate is provided, the method comprising providing a substrate to an electroplating apparatus, the substrate comprising a semiconductor comprising a plurality of features recessed into a surface of the substrate. providing a substrate, which is a substrate; immersing the substrate in an electrolyte of an electroplating apparatus; in a first stage, electroplating a material onto the substrate while flowing an electrolyte in or through an electroplating apparatus to provide a medium convection condition or a high convection condition to the surface of the substrate; switching from the first stage to the second stage when the first switching condition is satisfied; In a second stage, electroplating a material on the substrate while flowing an electrolyte in or through the electroplating apparatus to provide ultra-low convection conditions to the surface of the substrate, wherein in the ultra-low convection conditions, The electrolyte flow proximal to the surface of the substrate is laminar, the mass transport of metal ions in the electrolyte within the features is predominantly diffusion rather than convection over at least 75% of the depth of the features, and the medium convection condition or high convection condition is an ultra-low convection condition. provides greater convection to the surface of the substrate compared to and removing the substrate from the electrolyte.

In certain implementations high convection conditions are applied during the first stage, wherein (i) the electrolyte flow proximate the surface of the substrate is turbulent, and/or (ii) the flow proximate the surface of the substrate is The rate of electrolyte flow is within about 10% of the rate at which turbulence is achieved. In certain implementations moderate convection conditions are applied during the first stage, at which the mass transport of metal ions in the electrolyte within the features is predominantly diffusion rather than convection over about 50% or less of the depth of the features.

The first switching condition may be satisfied when the electrolyte sufficiently diffuses into the features. In these or other cases, the first switching condition may be satisfied when the current applied to the substrate is less than or equal to the limiting current experienced when switching to the second stage. In these or other cases, the first switching condition may be satisfied when at least the organic plating additives including the inhibitor are stabilized within the features. In certain implementations, the first switching condition is: (a) the electrolyte is sufficiently diffused into the features, (b) the current applied to the substrate is less than or equal to the limiting current that will be experienced when switching to the second stage, and (c) ) may be satisfied when organic plating additives, including at least an inhibitor, are stabilized within the features.

In some embodiments, the method includes switching from the second stage to the third stage when the second switching condition is met; and in a third stage, electroplating a material onto the substrate while flowing an electrolyte in or through the electroplating apparatus to provide a medium convection condition or a high convection condition to the surface of the substrate. In some such cases, the features may include a first feature and a second feature, the first feature having a wider CD compared to the second feature, and each of the first and second features from a common reference plane. With an instantaneous height when measured, the second switching condition is satisfied when a difference between the instantaneous height of the second feature and the instantaneous height of the first feature reaches the target height gap. The target height gap may be at least about 0.5 μm, or in certain cases at least about 1 μm. In some cases, the CD of the first feature may be at least about 20 μm wider than the second feature, and the target height gap may be at least about 2 μm. In various embodiments, the second switching condition considers a target that is within a wafer non-uniformity with respect to the substrate. As noted above, in various embodiments the features include a first feature and a second feature, the first feature having a wider CD compared to the second feature. The first feature may have a greater depth compared to the first feature. In other cases, the first feature may have a shallower depth compared to the first feature. In still other cases, the first feature and the second feature may have the same depth.

In certain implementations, the features may be defined in a photoresist layer, and the method may include, after removing the substrate from the electrolyte, forming a cap layer over the material deposited in the features; After forming the cap layer, removing the photoresist from the surface of the substrate; and reflowing the cap layer. In some such cases, after the cap layer is reflowed, the height gap between the first feature and the second feature may be less than before the cap layer is reflowed, the height gap measured from the common reference plane being the height gap of the first feature. It is measured as the distance between the instantaneous height and the instantaneous height of the second feature. In some cases, the height gap between the first and second features before the cap layer is reflowed may be at least about 2 μm, and the height gap between the first and second features after the cap layer is reflowed. The height gap may be about 0.5 μm or less. For example, after the cap layer is reflowed, the height gap between the first and second features may be about 0.1 μm or less.

In another aspect of the disclosed embodiments, an apparatus is provided. An apparatus may be configured to perform any of the methods described herein. In some implementations, an apparatus for electroplating a material on a substrate includes an electroplating chamber; substrate support; and a controller which causes a substrate to be provided to the electroplating apparatus, wherein the substrate is a semiconductor substrate including a plurality of features recessed into a surface of the substrate; causing the substrate to be immersed in an electrolyte in an electroplating apparatus; In a first stage, a material is electroplated onto the substrate while flowing an electrolyte into or through the electroplating apparatus to provide a medium convection condition or a high convection condition to the surface of the substrate; switch from the first stage to the second stage when the first switching condition is satisfied; In a second stage, the material is caused to be electroplated on the substrate while flowing the electrolyte in or through the electroplating apparatus to provide ultra-low convection conditions to the surface of the substrate, and the substrate is configured to be removed from the electrolyte; , at ultra-low convection conditions, the electrolyte flow adjacent the surface of the substrate is laminar, the mass transport of metal ions in the electrolyte within the features is predominantly diffuse rather than convective over at least 75% of the depth of the features, and moderate convection conditions. Alternatively, the high convection condition provides greater convection to the surface of the substrate compared to the ultra-low convection conditions.

These and other features will be described below with reference to the associated drawings.

1A-1D illustrate a number of partially filled features on a substrate.
1E-1H show top-down views of a number of different features that may be formed on a substrate.
2 , Panels A-H show two different features repeated at two different locations on a substrate as the features pass through various stages of processing according to certain embodiments.
3A-3C are flowcharts illustrating electroplating methods using at least one stage of ultra-low convection conditions in accordance with certain embodiments.
4A-4F show example combinations of different features, wherein the features are oriented differently from one another, that may be provided on a substrate according to certain embodiments.
5A-5D show a substrate with two different features on top as the substrate rotates through different positions during electroplating.
6A and 6B show plots for mixed CD features and mixed CD features when standard high convection is used (FIG. 6A) and when mixed convection as described herein is used (FIG. 6B). Experimental results showing the bump height distribution are shown.
7 and 8 show simplified diagrams of electroplating cells according to certain embodiments.
9 illustrates a simplified top-down view of a multi-tool electroplating apparatus in accordance with certain embodiments.

In this application, the terms "semiconductor wafer", "wafer", "substrate", "wafer substrate", and "partially fabricated integrated circuit" are used interchangeably. One skilled in the art will understand that the term "partially fabricated integrated circuit" can refer to a silicon wafer during any of the many stages of integrated circuit fabrication thereon. Wafers or substrates used in the semiconductor device industry typically have a diameter of 200 mm, or 300 mm, or 450 mm. Also, "electrolyte," "plating bath," "bath," and "plating solution" are used interchangeably. The detailed description below assumes that the present embodiments are implemented on a wafer. However, the present embodiments are not so limited. A workpiece may be of various shapes, sizes, and materials. In addition to semiconductor wafers, other workpieces that may take advantage of the disclosed embodiments are various articles such as printed circuit boards, magnetic recording media, magnetic recording sensors, mirrors, optical elements, micro-mechanical devices, and the like. include them

In the following description, numerous specific details are set forth to provide a thorough understanding of the presented embodiments. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail so as not to unnecessarily obscure the disclosed embodiments. Although the disclosed embodiments will be described in conjunction with specific embodiments, it will be understood that this is not intended to limit the disclosed embodiments. For example, various embodiments herein have been presented in the context of wafer-level packaging (WLP) applications. However, the concepts can be applied to many different electroplating applications. Similarly, although many of the embodiments herein are presented in the context of copper electroplating, the concepts can be applied to electroplating any metal. Other exemplary metals that may be plated include tin, tin-silver alloys, nickel, gold, cobalt, and combinations of these metals.

In various electroplating applications, convective conditions within the bulk electrolyte can have a significant impact on electroplating results. Convection conditions in the bulk electrolyte may be particularly relevant in cases where the features to be filled are relatively wide (eg, with CDs of about 5 to 300 μm for WLP applications). In many embodiments herein, convection conditions within the electrolyte are tailored to achieve high quality electroplating results. In many cases, electroplating occurs using at least one ultra-low convection stage.

As used herein, diffusion boundary distance (δ) is defined as the distance of metal ions in the electrolyte from the feature surface (eg, feature bottom) that can be considered the bulk metal ion concentration in the electrolyte. The diffusion boundary distance is also known as the Nernst diffusion layer thickness. At distances greater than δ, the metal ion concentration is estimated as the metal ion concentration of the bulk electrolyte. Conversely, at distances less than δ, there is a diffusion gradient that can be estimated as a linearly decreasing concentration gradient with the highest metal ion concentration at δ and the lowest metal ion concentration at the feature surface. This concentration gradient drives the diffusion of metal ions into the features, which are plated on the substrate surface, to the substrate surface. Diffusion is the main mechanism for the transport of metal ions, overcoming convective and migration effects at distances smaller than δ.

The diffusion boundary distance, δ, can be approximated for a particular feature as a plane parallel to the surface of the feature, such that a true planar diffusion boundary will result in the same average metal ion concentration at the surface of the feature. In other words, the diffusion length varies across the surface of each feature due to mass transport occurring and fluctuations in the convective profile within the feature. For simulation purposes, a single diffusion boundary distance, δ, may be used in each feature and corresponds to the distance from the feature surface to the plane at the overall bath concentration that results in the same average concentration of metal ions at the feature surface due to diffusion. The surface of the feature under consideration is the bottom surface of the feature (not the sidewalls or field area). With these simplifications, the diffusion near the substrate can be treated/estimated as a 1D diffusion condition.

There are a number of factors that affect the plating rate within a feature. These factors include, but are not limited to, the voltage applied to the surface of the feature (sometimes referred to as an overpotential), the temperature of the electrolyte and substrate, the concentration and identity of additives in the electrolyte (e.g., accelerators, inhibitors, leveler, etc.), metal ion concentration in the electrolyte, convection conditions in the electrolyte, and the like. All other factors being equal, the plating rate is proportional to the metal ion concentration at the surface of the feature. Typically, for smaller δ, the metal ion concentration at the surface of the feature is relatively higher, and for larger δ, the metal ion concentration at the surface of the feature is relatively lower. A larger δ results in a lower metal ion concentration at the feature surface, since a larger δ provides a longer distance for the metal ion concentration to decrease linearly. The result is a higher plating rate at smaller δ and vice versa.

This difference in plating rate can be a problem in cases where the substrate includes features of different sizes. Features of different sizes have different diffusion boundary distances. As such, features of different sizes (with different δ) are provided near each other on the substrate, and features with smaller δ tend to plate faster. This difference in plating rate results in poor uniformity (eg, high within-die non-uniformity) of the plated features. Within-die non-uniformity relates to the uniformity of plated features within a single die on a substrate. A single substrate typically includes many dies. A single die may include multiple feature sizes and/or shapes.

One conventional way to address intra-die non-uniformity arising from different feature sizes/shapes is to employ very high convection conditions. Higher convection conditions increase the flow rate of the electrolyte through the electroplating apparatus, allow for faster mixing of the electrolyte within the electroplating apparatus (e.g., using paddles, shear plates, etc.) , moving (eg, spinning) the substrate more rapidly within the electrolyte, and the like. These high convection conditions reduce δ for most or all of the features because they allow metal ions to diffuse better towards the surface of the features. High convection conditions are also considered advantageous because they promote high plating rates, which result in high throughput. In the extreme case where convection is infinite, δ collapses to zero for all features, and features of different sizes will all plate at the same rate. In practice, it is not possible to achieve infinite convection. Moreover, this method is less effective if deeper (eg, higher aspect ratio) features are formed in the substrate.

In embodiments herein, a different approach is used to achieve acceptable intra-die non-uniformity in cases where a substrate includes multiple feature sizes. In contrast to using high convection conditions, the methods herein use an ultra-low convection stage. These methods have unexpectedly been demonstrated to achieve improved within-die non-uniformity. These results were not expected for the reasons described above, at least generally resulting in a shift to higher convective conditions for these applications in the industry (eg, for uniformity reasons as well as throughput reasons). Moreover, the results were unexpected since previous studies have demonstrated that low convection plating stages (as opposed to ultra-low convection plating stages as described herein) typically produce very poor plating results. By carefully tailoring the convection conditions over the course of the electroplating process using the techniques described herein, unexpectedly high quality plating results could be achieved even when the substrate contains different feature sizes within a single die. .

As used herein, the term ultra-low convection refers to laminar flow (or substantially stagnant) of the electrolyte near the substrate, with mass transport of metal ions in features on the substrate over at least 75% of the depth of the features. Refers to conditions in which diffusion rather than convection predominates. Conversely, the term high convection refers to conditions in which the electrolyte near the substrate has a rate very close to or exceeding the onset of turbulence (eg, within about 10% of the rate at which turbulent flow is achieved). The term moderate convection conditions refers to conditions in which 50% or less of the features are predominantly diffusion rather than convection and the electrolyte near the substrate has a rate at least 10% less than the rate at which turbulent flow is achieved. The term low convection conditions refers to conditions in which about 50-75% of the features are non-convective but diffusional predominates.

During the ultra-low convection stage, δ becomes relatively large for all of the different features reaching the top of the feature (eg, reaching the top of the photoresist in which the feature is defined). Although the overall plating rate during the ultra-low convection stage is lower than in the high convection cases, the relative difference in δ between differently sized features can be reduced. For example, features that start with a relatively larger δ may exhibit a smaller rise in δ, and features that start with a relatively smaller δ may exhibit a larger rise in δ, resulting in differently sized features. equalize δ among them. This reduction in the relative difference of δ between differently sized features means that the differently sized features can plate at a more uniform rate during the ultra-low convection stage.

An ultra-low convection stage is particularly advantageous when used in combination with other convection conditions throughout the electroplating process. By tailoring convection conditions throughout the plating process, high quality plating results can be achieved.

It is advantageous to include an ultra-low convection stage early in the electroplating process. To some extent, the earlier the ultra-low convection stage is initiated, the more uniform the uniformity of the plated features. However, in some applications, the ultra-low convection stage may be started after the initial plating stage where medium or high convection conditions are used. This initial plating stage may be used to ensure that plating additives are properly dispersed into the features (eg, to promote a bottom-up fill mechanism) and/or to avoid issues related to limiting current. may be The limiting current is the maximum plating current that can be applied to the substrate under the relevant plating conditions. The limiting current occurs because metal ions cannot be deposited on the substrate faster than the metal ions reach the surface of the substrate. Above the limiting current, the metal ions near the substrate surface are depleted, and the metal ions are insufficient to sustain the current to be applied to the substrate. As a result, unwanted side reactions such as generation of hydrogen gas become a problem. Below the current limit, there are sufficient metal ions in the vicinity of the substrate to sustain the current to be applied to the substrate, and unwanted side reactions are minimized or prevented.

The limiting current varies over the course of the electroplating process. If all other factors are equal, the limiting current starts to rise over the course of electroplating a single substrate. As such, the initial part of the electroplating process is most sensitive to limiting current conditions (because the limiting current is lowest at this time). Convection conditions affect the value of limit current, with higher convection conditions corresponding to higher limit current and vice versa. As such, to avoid limiting current conditions during the initial stage of electroplating, ultra-low convection conditions may be avoided during the initial stage in some implementations. Instead, medium convection conditions or high convection conditions may be used at this time. This initial intermediate convection stage or high convection stage may promote the formation of a strong base for the plated features.

In some embodiments, a medium convection stage or high convection stage may be used in the final portion of electroplating on the substrate. Although ultra-low convection conditions advantageously result in low intra-die non-uniformity, these conditions also result in a lower overall plating rate. A lower overall plating rate reduces throughput because plating each substrate takes longer. The use of a medium convection stage or high convection stage can increase the overall plating rate, thereby improving throughput. Medium convection stages or high convection stages may also be used to promote certain types of uniformity that may be experienced in cases where ultra-low convection is used too long (e.g., to reduce within-wafer non-uniformity resulting from non-uniform photoresist deposition). ) may be advantageous.

Although the disclosed embodiments do not require the use of a medium or high convection stage, such stages can improve electroplating results when used in combination with an ultra-low convection stage. The time(s) at which the convection conditions switch from one convection stage to another can affect the order of the different stages as well as the electroplating results.

The optimal time for switching between an early medium or high convection stage and a later ultra-low convection stage is based on several considerations. For example, plating is performed by: (1) sufficient diffusion of the plating solution into the features after immersion of the substrate; (2) the plating current is sufficiently lower than the limiting current of ultra-low convection conditions; and/or (3) switching from the initial medium convection stage or high convection stage to the ultra-low convection stage when one or more of the conditions under which the plating additives are stabilized are met. In some cases, plating switches from an initial medium convection stage or high convection stage to an ultra-low convection stage when any two of these conditions are met or when all three of these conditions are met.

For diffusion of the plating solution into the features after immersion of the substrate, this diffusion typically occurs over a period of about 1 to 10 seconds, depending on the dimensions of the features and the convection conditions that exist within the plating cell. Higher aspect ratio features typically result in longer diffusion time frames. Greater convective conditions typically result in shorter diffusion time frames.

For plating current, it is important to avoid exceeding the limiting current when ultra-low convection conditions are applied. As described above, the limiting current is lower when ultra-low convection is used compared to higher convection conditions. The limiting current also rises as material is plated into the features and the depth of the features decreases. In some cases, the current applied to the substrate may change between an initial intermediate or high convection stage and a subsequent ultra-low convection stage. For example, the magnitude of the plating current may be reduced prior to or simultaneously with ultra-low convection conditions being applied. In other cases, the current applied to the substrate remains constant between the initial intermediate or high convection stage and the subsequent ultra-low convection stage. Regardless of whether the applied current is uniform between these stages, it is important to ensure that the plating current applied to the substrate during the ultra-low convection stage is below the limiting current during this stage. In cases where the plating current is uniform between these stages, the decision when to switch between stages is based on the limiting current applied to the substrate towards the end of the initial medium convection stage or high convection stage compared to the limiting current of the ultra-low convection conditions. It may also be based on plating current. In one example, plating switches from the initial medium convection stage or high convection stage to the ultra-low convection stage when the plating current is less than or equal to about 50% of the limit current for ultra-low convection conditions. In another example, plating switches from an initial medium convection stage or high convection stage to an ultra-low convection stage when the plating current is less than or equal to about 90% of the limit current for ultra-low convection conditions. If a 50% threshold is used, the risk of encountering limiting current problems is very small. If the 90% threshold is used, the risk of encountering limiting current problems is greater, but acceptable.

Regarding stabilization of the plating additives, this typically occurs over a duration of about 0 to 5 minutes, depending on the identity of the plating additives and their associated adsorption/desorption properties. This consideration is highly dependent on the exact chemistry used, as well as the material being plated.

The optimal time to switch from the ultra-low convection stage to the final intermediate or high convection stage is also based on several considerations. In various cases, the optimal time for this switching is based on balancing certain performance tradeoffs. In some cases, this switching time is selected to optimize intra-die uniformity (WiD%), as described with respect to FIG. 2 where multiple feature shapes/sizes are provided on a single die. This uniformity is taken into account after the tin or tin-silver cap is plated and then reflowed over the different features. Because solder reflows differently across differently sized/formed features, it may be desirable to plate each of the features to different bump heights prior to deposition of a tin or tin-silver cap. The time the plating switches from the ultra-low convection stage to the final intermediate or high convection stage affects the relative bump heights for different features.

In a specific example, the substrate includes feature A and feature B. Feature A has a wider CD than feature B. Plating conditions may be changed from an ultra low convection stage to a final intermediate convection stage or a high convection stage when a certain height gap is achieved between features. This height gap is measured as shown by element 211 in panels C and D of FIG. 2 and is calculated as the height of feature B minus the feature height (as measured from the common reference plane). In cases where feature A is deeper than feature B, this height gap increases with time when ultra-low convection conditions are applied. Conversely, in cases where feature A is shallower than feature B, the height gap decreases with time when ultra-low convection conditions are applied. The behavior in the ultra-low convection regime is opposite to that seen in the high convection regime. Specifically, when high convection conditions are used, the height gap always tends to decrease with time, making targeting the desired height gap difficult or impossible in many cases. In certain embodiments, the plating conditions are changed from an ultra-low convection stage to a final intermediate convection stage or high convection stage when the gap height reaches the target gap height. Examples of target gap heights for different feature sizes and different tin or tin-silver cap thicknesses are provided below in Table 1.

CD of feature A
(μm) Feature B's CD
(μm) Sn(Ag) thickness before reflow (㎛) Target gap height (μm) 60 40 10 1.5 60 50 10 0.6 50 30 10 2.3 50 40 10 0.9 40 20 10 3.5 40 30 10 1.4 60 40 15 2.9 60 50 15 1.3 50 30 15 4.0 50 40 15 1.7 40 20 15 5.5 40 30 15 2.3 60 40 15 4.2 60 50 20 1.9 50 30 20 5.4 50 40 20 2.4 40 20 20 7.2 40 30 20 3.1

These target gap heights are expected to result in uniform feature heights after deposition and reflow of the tin or tin-silver solder cap (eg, between wider feature A and narrower feature B). The CDs listed in Table 1 relate to the diameters of circular features. For non-circular features, target gap heights may be shifted compared to circular features with similar CDs. The examples provided in Table 1 relate to current state of the art features used in semiconductor fabrication, but the embodiments are not limited thereto. The techniques described herein may be practiced using any feature sizes or combination of feature sizes.

Based on the examples in Table 1, in some embodiments feature A has a CD that is at least about 10 μm wider than feature B, eg at least about 20 μm wider than feature B. In various cases, feature A has a CD that is about 5 to 30 μm wider than feature B, eg, about 10 to 20 μm wider than feature B. In some cases, the CD of feature B is between about 50 and 85% of the CD of feature A. In these or other cases, the tin or tin-silver solder cap may be provided to a thickness of about 5 to 30 μm, such as about 10 to 20 μm. In these or other cases, the target gap height may be between about 0.5 and 10 μm, such as between about 1 and 8 μm, or between about 1 and 5 μm, or between about 1 and 3 μm. In certain cases, the target gap height is about 0.5 to 2 μm, about 1 to 2 μm, about 2 to 3 μm, about 3 to 4 μm, about 4 to 5 μm, about 5 to 6 μm, about 6 to 7 μm, about 7 to 8 μm, or the like. In certain examples, the CD of feature A is about (or at least about) 20 μm wider than the CD of feature B, and the target gap height is at least about 2.0 μm (between about 2.0 and 8.0 μm in some cases). As shown in Table 1, the optimal target gap height varies with various features and layer geometries.

By using the target gap height to determine when to switch from the ultra-low convection stage to the final intermediate or high convection stage, in-die non-uniformity is minimized/optimized. However, in certain cases, this focuses on the target gap height and intra-die non-uniformity can result in unacceptably high intra-wafer non-uniformity. Intra-wafer non-uniformity is a measure of the non-uniformity between different dies on different parts of a substrate (e.g., areas where the photoresist is thicker and the features are deeper, and areas where the photoresist is thinner and the features are shallower). . Conversely, intra-die non-uniformity is a measure of the non-uniformity of features within a single die, located at specific locations on a substrate. As such, the target gap height may be used to determine when to switch from an ultra-low convection plating stage to a subsequent intermediate or high convection stage in cases where the intra-wafer non-uniformity that occurs is at an acceptable level. Given the target gap height in cases where within-wafer non-uniformity is unacceptably high (e.g., greater than about 5%), the decision to switch from an ultra-low convection stage to a subsequent intermediate or high convection stage is Instead, it may be selected to achieve non-uniformity within the target wafer (eg, <5%). This may result in switching to either a medium convection stage or a high convection stage before reaching the target gap height. Higher convection conditions tend to improve within-wafer non-uniformity.

The techniques described herein can be used in any electroplating application. However, the disclosed techniques: (1) the substrate contains features with different CDs, but the same depth; (2) the substrate has features with different CDs, and features with wider CDs are deeper than features with narrower CDs; (3) the substrate includes features with different CDs, where features with wider CDs are shallower than features with narrower CDs; (4) the substrate includes features with the same CD, one feature being deeper than the other; or (5) the substrate includes features having a longer axis and a shorter axis (eg, features that are oblong or rectangular), and certain features are oriented differently on the substrate. It is particularly advantageous in cases where certain conditions are met.

In various applications, a substrate will include features of two or more sizes and/or shapes within a single die. In some embodiments, the features may have CDs ranging from about 5 to 300 μm, depths ranging from about 5 to 300 μm, and depth:width aspect ratios from about 0.5:1 to 3:1. For applications involving plating through photoresist, typical CDs are about 20-80 nm, and typical depth:width aspect ratios are about 1:1 to 2:1. Feature openings are typically round, rectangular, or rectangular (although any shape may be used). Prior to plating, different features may be of different depths or the same depth. In cases where the features start at different depths, the difference in depths is typically about 10 μm or less. Similarly, different features may have different CDs, or the same CDs.

In certain embodiments, the substrate includes a first feature and a second feature on the same die, the first feature and the second feature having different CDs, depths, and/or shapes. In one embodiment, the first feature has a depth that is at least about 1.1x the depth of the second feature (e.g., the first feature has a depth of 50 μm and the second feature has a depth of at least about 55 μm). ). In some cases, the first feature has a depth that is at least about 1.5x the depth of the second feature. In these or other cases, the first feature may have a CD that is at least about 1.5x the CD of the second feature (or vice versa). In some such cases, the first feature may have a CD that is at least about 2x the CD of the second feature (or vice versa). In these or other cases, the first feature may have an aspect ratio that is at least about 1.5x the aspect ratio (depth/width) of the second feature (or vice versa). In some such cases, the first feature has an aspect ratio that is at least about 2x the aspect ratio of the second feature (or vice versa). In these or other cases, the first feature shape and the second feature shape may be rectangular or elliptical (when viewed from above), and the longer dimension of the first feature does not align with the longer dimension of the second feature. In some cases the longer dimension of the first feature is perpendicular to the longer dimension of the second feature. In some other cases, the first feature is rectangular or oval, and the second feature is square or circular.

1A illustrates a partially filled feature 102a on a substrate 101 . Feature 102a is defined in photoresist 103, which is patterned to form feature 102a. A seed layer 104 is provided over the substrate 101 . Feature 102a is partially filled with plated metal 105 . The CD of the feature is labeled 106, and the depth of the feature (after being partially filled, as shown) is labeled 107. It is understood that the depth of the feature is greater than before plating occurs. The aspect ratio of feature 102a is depth 107 divided by CD 106.

1B-1D illustrate additional example features 102b, 102c, and 102d, which may be used in some cases. These features differ from the features shown in FIG. 1A by including an electrically insulating material 110 . This electrically insulating material may be, for example, polyimide (PI) or photosensitive polyimide (PSPI). Additionally, the features shown in FIGS. 1B and 1C have a non-flat seed layer 104 . Feature 102d shown in FIG. 1D has an electrically insulating material 110 across the entire lower end of the feature. The electrically insulating material 110 will electrically isolate the plated metal 105 of the feature 102d after the photoresist and seed edges are removed in subsequent processing. Feature 102d of FIG. 1D is an example of a feature that may be used primarily for structural, but not electrical, purposes in an end device.

1E-1H are top-down views of different feature shapes. The feature in FIG. 1E is circular, the feature in FIG. 1F is ovoid, the feature in FIG. 1G is square, and the feature in FIG. 1H is rectangular.

It may be desirable to electroplate such that the resulting features (eg, pillars) all have the same bump height as measured from a common reference plane after plating. In some other cases, it may be desirable to electroplate relatively narrower features to have a taller bump height after plating, compared to relatively wider features. This difference in bump height is because material subsequently deposited on plated features (e.g., tin or tin-silver cap) may reflow differently on differently sized features during later processing. may be advantageous. For example, a narrower SnAg cap on a narrower plated pillar will lose more height when the SnAg cap is reflowed compared to a wider SnAg cap on a wider plated pillar. Thus, to achieve uniform heights after reflow of SnAg caps, it is advantageous to ensure that the narrower feature is plated to a longer height than the wider feature. This result is difficult to achieve using conventional electroplating techniques because narrower features are typically plated at a lower rate than wider features (particularly in cases where narrower features are narrower than wider/deeper features). difficult or impossible However, the disclosed ultra-low convection plating stage described herein can be used to achieve this difficult and desirable result.

2 illustrates feature A and feature B as they undergo various processing stages. FIG. 2 serves to illustrate why it may be advantageous to plate narrower features and wider features simultaneously in certain embodiments, where a narrower feature is plated with a longer bump height compared to a wider feature. FIG. , feature A and feature B are provided together on a single die. The die is repeated across the face of the substrate, including regions with normal thickness photoresist and regions with relatively thicker (eg, longer) photoresist. In areas with thicker photoresist, the recessed features formed in the photoresist are relatively deeper when compared to areas with thinner/conventional photoresist. In FIG. 2, panel A, panel C, panel E, and panel G show features of a die located in an area with a typical photoresist thickness, while panel B, panel D, panel F, and panel H show more Shows features of the die located in areas with thick photoresist. Feature A has CD 206a and feature B has CD 206b. CD 206a and CD 206b are different from each other, but are uniform among different areas on the substrate (eg, CD 206a in panel A is the same as CD 206a in panel B).

As shown in Panels A and B, prior to electroplating, the substrate 201 includes a seed layer 204 and a patterned photoresist 203 layer thereon. Photoresist 203 defines recessed features to be filled. In this example, feature A is wider and deeper than feature B. As shown in panels C and D, after electroplating copper 205 into the features, there is a height gap 211 . This height gap 211 represents the difference in height between features A and B as measured from a common reference plane. The height gap 211 implemented should be uniform between different regions on the substrate (eg, the height gap 211 of panel C may be the same as the height gap 211 of panel D). As mentioned above, this height gap 211 has been difficult or impossible to achieve in many cases using conventional plating techniques. However, this height gap 211 can be realized by including an ultra-low convection stage as described herein.

After copper 205 is electroplated into the features, tin or tin-silver material 206 is deposited after copper 205, as shown in Panels E and F. Tin or tin-silver material 206 may form a cap on copper 205 . Tin or tin-silver material 206 may be deposited using conventional techniques in some cases. In other cases, tin or tin-silver material 206 may be deposited using techniques described herein, for example, by including an ultra-low convection stage. The height gap 211 may remain substantially during deposition of the tin or tin-silver material 206 (although it may shrink or grow in some cases). After deposition of the tin or tin-silver material 206, the substrate undergoes various processing steps to strip away the photoresist, clean the seed edges, and reflow the tin or tin-silver material 206. suffer from After reflow, the tin or tin-silver material 206 has a dome shape as shown in panels G and H. As described above, the narrower feature B is reflowed/reduced to a greater degree than the wider feature A. Because feature B was initially plated with copper 205 to a longer bump height (using a common reference plane) than feature A, feature A and feature B are of uniform bump height after the reflow operation. This uniform bump height is the same across all areas of the substrate as shown by the dotted line extending from panel G to panel H. In various embodiments, there may be layers of other metals or other materials provided between copper 205 and tin or tin-silver material 206 . For example, nickel is commonly used between these layers. In certain examples, the feature includes a stack having the order copper/nickel/tin, or copper/nickel/tin-silver. In another embodiment, an additional layer of copper may be provided. In some such embodiments, the feature includes a stack having the order copper/nickel/copper/tin, or copper/nickel/copper/tin-silver.

In many cases, the final intra-die non-uniformity after a reflow operation may be calculated for a particular substrate (eg, when the substrate is as shown in Panel G and Panel H). At this time, when all features are measured from a common reference plane, it is desirable to have a uniform bump height.

In certain embodiments, it may be advantageous to vary the current and/or potential applied to the substrate throughout the electroplating process. In some cases, the substrate may be immersed at a constant potential (eg, between the substrate and the reference electrode). In some other cases, the substrate may be immersed with a constant current or constant current density. In some cases, the current or current density may ramp up (continuously or stepwise) as the substrate is immersed. In some cases, the substrate may be immersed without application of current or potential to the substrate. Substrate immersion is further discussed in U.S. Patent Nos. 6,793,796, and 9,385,035, each of which is incorporated herein by reference in its entirety.

After the substrate is immersed, the current and/or potential applied to the substrate may be changed. In many cases, the substrate may be electroplated at a constant current density or constant potential. In some cases, the substrate may be electroplated at a first current density or potential, followed by a second current density or potential, etc., where different current densities/potentials are applied at different stages of plating.

The current and/or potential applied to the substrate during plating may vary independently of convection conditions. However, in some cases, current and/or potential may vary with convection conditions. In these cases, the current and/or potential applied to the substrate changes simultaneously as the convection conditions change.

3A-3C show flowcharts illustrating electroplating methods using the low convection techniques described herein. Method 300a of FIG. 3A is the simplest method. Method 300a begins at operation 301 where a substrate having first and second features is received in an electroplating apparatus. The first feature and the second feature are different from each other, eg, have different CDs and/or depths as described above. The first feature and the second feature may be provided together on a single die. The die may be repeated over the surface of the substrate. Next, in operation 303 the substrate is immersed in an electrolyte. The substrate may or may not rotate during immersion. Any convection conditions may be used during immersion. In certain instances, medium convection conditions or high convection conditions are used during immersion. In another example, ultra-low convection conditions are used during immersion. As mentioned above, the substrate may be anodized during immersion or may not be anodized, for example using a constant potential or constant current or current density in some cases.

At operation 305, metal is electroplated on the substrate while ultra-low convection conditions are applied. This is an ultra-low convection stage. As described above, a number of different factors influence convection conditions. For example, the flow rate of the electrolyte through the electroplating cell, the rotation rate of the substrate, the rate at which the mixer spins/moves in the electrolyte, and the temperature of the electrolyte and/or substrate can all affect the convection conditions. Some of these factors (eg rotation rate) may be easier to control/regulate than others (eg temperature of the electrolyte).

During the ultra-low convection stage, the diffusion boundary distance, δ, is relatively large for both the first and second features. In some cases, δ may reach the height of the photoresist, causing δ to be relatively uniform for the first and second features. As a result, the first and second features are plated at a substantially uniform rate. This is especially true when the first feature and the second feature are of similar depths. Conversely, in cases where the first feature and the second feature have different depths (and especially if the feature has a wider CD that is deeper than a feature with a narrower CD), δ can be smaller on the narrower feature, This promotes faster plating within narrower features compared to wider features. This phenomenon has been difficult or impossible to achieve using other methods. Next, in operation 309, the substrate is removed from the electrolyte and method 300a is complete.

The method 300b shown in FIG. 3B is similar to the method 300a of FIG. 3A , and only the differences will be discussed for brevity. After the substrate is immersed in operation 303, the method 300b continues with operation 304 where metal is electroplated on the substrate while either a medium convection condition or a high convection condition is applied. This initial intermediate convection stage or high convection stage may be useful for establishing bottom-up fill, ensuring that electroplating additives are properly dispersed into features, depositing metal while the limiting current is particularly low, and the like. After the medium convection condition or high convection condition is applied at operation 304, the method continues at operation 305 where the ultra-low convection conditions are applied. The remaining aspects of method 300b of FIG. 3B are similar to those described with respect to method 300a of FIG. 3A.

Method 300c of FIG. 3C is similar to method 300b of FIG. 3B. For the sake of brevity, only differences will be described. After ultra-low convection conditions are applied in operation 305, it may be determined whether the electroplating process is complete. If yes, the method continues to operation 309 where the substrate is removed from the electrolyte. In this case, method 300c simplifies method 300b of FIG. 3B. If electroplating is not yet complete at operation 306, method 300c continues to operation 307 where either a medium convection condition or a high convection condition is applied. Convection conditions may be the same as or different from the conditions applied during operation 304 . In some cases, the medium convection condition or high convection condition applied during operation 307 may counteract certain intra-wafer non-uniformities that may occur as a result of non-uniform photoresist deposition. Moreover, the medium convection condition or high convection condition applied during operation 307 may increase throughput when compared to a process that proceeds without such operation.

Next, at operation 308, it may be determined whether the electroplating process is complete. If yes, the method continues to operation 309 where the substrate is removed from the electrolyte. If plating is not yet complete, the method 300c continues to operation 305 where ultra-low convection conditions are again applied while metal is being electroplated onto the substrate. The ultra-low convection conditions and the medium or high convection conditions applied in operations 305 and 307, respectively, may be repeated until electroplating is complete and the substrate is removed from the electrolyte.

In a particular example, method 300c involves an initial intermediate or high convection stage (act 304), a single ultra-low convection stage (act 305), and a final intermediate or high convection stage (act 307). In another example, method 300c includes a plurality of intermediate convection stages occurring between an initial intermediate convection stage or high convection stage (act 304), a plurality of ultra-low convection stages (act 305), and repeated ultra-low convection stages. or high convection stages (act 307). Convection stages may be repeated/cycled any number of times. In another example, operation 304 of method 300c may be omitted such that ultra-low convection conditions are applied during or immediately after immersion.

As mentioned above, in some cases the current applied to the substrate may vary throughout the electroplating process. In one example, method 300b or method 300c may include applying a relatively lower current to the substrate during the ultra-low convection stage at operation 305, and during the middle or high convection stage at operation 304 and/or operation 307. It involves applying a relatively higher current to the substrate. In a particular example, the method 300c includes the act of applying a relatively low current to the substrate during an initial intermediate convection stage or high convection stage at act 304 (e.g., while the threshold current is relatively low), ultra-low convection at act 305. This entails applying a relatively low current to the substrate during the stage and, in operation 307, applying a relatively higher current to the substrate during the medium convection stage or high convection stage.

In some embodiments, the current may rise slowly over time during the ultra-low convection stage. The current may be controlled to stay near but below the limit current. In one example, the applied current is controlled to about 85-95% (eg, about 90% in some cases) of the instantaneous limit current during the ultra-low convection stage. As plating progresses and features become shallower, the limiting current rises as the applied current rises.

[Inventors- Is there anything specific to add regarding the regulation of current/potential? Can there be some specific examples for different combinations of feature types?]

In one implementation, the first feature and the second feature are oriented differently and the convection conditions are varied over time to affect the different features differently. 4A-4F show top-down views of substrates having different pairs of features exaggerated in size for illustrative purposes. Specifically, FIGS. 4A-4F show a number of examples where the first and second features are oriented differently on the substrate. Lines 415 and 416 are provided for the purpose of describing the orientation of various features. In FIG. 4A , the first feature 401 is rectangular and the second feature 402 is square. First feature 401 is oriented with a longer axis pointed along line 415 . In FIG. 4B , first feature 403 and second feature 404 are both rectangular, first feature 403 is oriented with the longer axis pointing along line 415 and second feature 404 is It is oriented along the longer axis pointed along line 416 . In this example, feature 403 and feature 404 are oriented perpendicular to each other. In FIG. 4C , first feature 405 is a rectangle oriented along the longer axis along line 415 and second feature 406 is a circle. In FIG. 4D , first feature 407 is a rectangle with its longer axis pointing along line 415 and second feature 408 is an ellipse with its longer axis pointing along line 416, wherein the first feature It is perpendicular to (407). In FIG. 4E , first feature 409 and second feature 410 are both elliptical, first feature 409 being oriented with the longer axis pointing along line 415 and second feature 410 being It is oriented with the longer axis pointed along line 416 and perpendicular to first feature 409 . In FIG. 4F , first feature 411 is an ellipse with the longer axis pointing along line 415 , and second feature 412 is circular. These combinations of features are provided as examples and are not intended to be limiting. Any combination of feature shapes and orientations may benefit from the techniques described herein.

In cases where the substrate is rotated during electroplating, convection conditions can be adjusted with the substrate rotation for better deposition in one feature than another. Different orientations of features, as well as directional flow through the electroplating cell, may contribute to this result. Where the flow through the electroplating cell has a directional cross-flow component (e.g., electrolyte flows from the inlet side to the outlet side, the inlet side and the outlet side flow across the substrate so that the electrolyte flows along the plating side of the substrate in a shearing fashion). located proximal to azimuthally opposed peripheral locations), relatively lower convection conditions (in some cases ultra-low convection conditions as described above) when these features are in the first position for cross flow The convection conditions may be adjusted such that relatively higher convection conditions (eg, intermediate convection conditions or high convection conditions) are applied when the features are in the second position with respect to cross flow. Electroplating cells with directional cross flow are further described in the following US patents and US patent applications, each incorporated herein by reference: US Patent No. 9,624,592 entitled "CROSS FLOW MANIFOLD FOR ELECTROPLATING APPARATUS"; US Patent Application Serial No. 14/924,124, filed on October 27, 2015, entitled "EDGE FLOW ELEMENT FOR ELECTROPLATING APPARATUS"; US Patent Application No. 15/161,081, filed on May 20, 2016, entitled "DYNAMIC MODULATION OF CROSS FLOW MANIFOLD DURING ELECTROPLATING", filed on August 1, 2016, entitled "DYNAMIC MODULATION OF CROSS FLOW MANIFOLD DURING US Patent Application Serial No. 15/225,716, "ELECTROPLATING"; US Patent Application Serial No. 15/413,252, filed January 23, 2017, entitled "MODULATION OF APPLIED CURRENT DURING SEALED ROTATIONAL ELECTROPLATING".

One example is described with respect to FIGS. 5A-5D. 5A-5D illustrate a substrate having a first feature 501 and a second feature 502, the first feature 501 and the second feature 502 being shaped as a rectangle and oriented perpendicular to each other. Line 516 represents the direction of cross flowing electrolyte across the plated side of the substrate. In FIG. 5A, the substrate is in a first orientation, in FIG. 5B, the substrate is in a second orientation rotated 90° clockwise from the first orientation, and in FIG. 5C, rotated 90° clockwise from the second orientation. is in a third orientation, and in FIG. 5D the substrate is in a fourth orientation rotated 90° clockwise from the third orientation. The substrate may be rotated through the different orientations shown in FIGS. 5A-5D as the electroplating process progresses.

When the substrate is in the first and third orientations, as shown in FIGS. 5A and 5C respectively, the electrolyte cross flow is aligned with the longer axis of the second feature 502 and the longer axis of the first feature 501. perpendicular to the long axis In these orientations, convective conditions preferentially affect the diffusion boundary distance, δ, for the second feature 502 compared to the first feature 501 . Conversely, when the substrate is in the second and fourth orientations as shown in FIGS. 5B and 5D respectively, the electrolyte cross flow is aligned with the longer axis of the first feature 501 and the longer axis of the second feature 502. perpendicular to the longer axis. In these orientations, convective conditions preferentially affect δ for the first feature 501 compared to the second feature 502 .

In various examples, convection conditions are adjusted as the substrate is rotated through different orientations for better deposition in one feature than another. In one example, ultra-low convection conditions are applied when the substrate is in the first and third orientations shown in FIGS. 5A and 5C respectively, and the substrate is in the second and fourth orientations shown in FIGS. 5B and 5D respectively. When in the orientation, medium convection conditions or high convection conditions apply. Ultra-low convection conditions raise δ in the features, but when ultra-low convection conditions are applied, δ in the second feature 502 is ) rises to a degree greater than my δ. Elevated δ slows the plating overall, resulting in preferentially slowed plating in the second feature 502 compared to the first feature 501 . Conversely, a medium or high convection condition lowers δ in the features, but when the medium or high convection condition is applied, since the electrolyte cross flow aligns with the longer axis of the first feature 501, the first feature δ in 501 is lowered by a greater degree than δ in second feature 502 . A lower δ increases the overall plating rate and preferentially increases the plating rate in the first feature 501 compared to the second feature 502 . As the substrate rotates and convective conditions cycle, these effects combine to produce a relatively higher plating rate within the first feature 501 and a relatively lower plating rate within the second feature 502 . These effects may be applied to any combination of features, including but not limited to the features shown in FIGS. 4A-4F.

In some cases, results in a more uniform bump height when measured from a common reference plane across features originating at different depths and/or CDs (compared to cases where convective conditions are not adjusted with substrate rotation). The same technique can be used to For example, if the electroplating process for a particular substrate results in an uneven bump height between two features with different initial depths and/or CDs, the electroplating process can adapt to the substrate rotation for good deposition of the feature. It may be modified to adjust convection conditions or it would be underplated. This same technique can be used to achieve a specific desired height gap between the metal plated on one feature and the metal plated on another feature. This may be desirable, for example, for the reasons described above with respect to FIG. 2 .

In cases where convection conditions are adjusted along with substrate rotation, it may be advantageous to choose a method of adjusting the convection conditions that affects the conditions relatively quickly. One simple way to quickly adjust the convection conditions is to raise and/or lower (or stop) the flow rate of electrolyte through the electroplating cell. Higher rates of electrolyte flow correspond to more substantial convection conditions. Another way to adjust the convection conditions is to increase and/or decrease the rate or frequency at which the substrate rotates, or the rate or frequency at which the spinner/paddle/mixer/shear plate within the electroplating cell rotates. Similarly, in cases where convection is caused by a paddle, shear plate or similar mixing mechanism, convection conditions may be affected by the distance between the mixing mechanism and the substrate. Generally, longer distances between the substrate and the mixing mechanism result in lower convection and vice versa. Another way to adjust the convection conditions is to adjust the relevant geometric dimensions of the electroplating apparatus. In some instances where the electrolyte flows through a narrow gap (eg, between the substrate and the ionic resistive element), changing the dimensions of the gap affects the convection conditions. Specifically, increasing the height of the gap results in lower shear rates/relatively lower convection conditions (assuming a constant electrolyte flow rate through the gap) at the substrate surface. Conversely, reducing the height of the gap raises the shear rate of the electrolyte near the substrate, thus providing relatively higher convective conditions (assuming a constant electrolyte flow rate through the gap). An exemplary device utilizing electrolyte flow through such a gap is described with respect to FIG. 8 . Other methods for controlling convection conditions have been described above.

Experiment

6A and 6B illustrate certain advantages of the jointly disclosed ultra-low convection electroplating techniques. Each of these figures shows the bump height distribution achieved on the tested substrate. Each of the figures also shows cross-sectional views of exemplary features after electroplating. The tested substrates included two different feature sizes. Feature A was an elliptical feature with an opening of about 45 μm×55 μm, and feature B was an elliptical feature with an opening of about 30 μm×40 μm. Both feature A and feature B were about 50 μm deep before plating.

6A shows a bump height distribution for a plated substrate in conventional high convection conditions. The two features are plated at different bump heights, with the wider feature A plating a longer bump height compared to the narrower feature B. 6B shows a bump height distribution for a substrate plated using the mixed convection techniques described herein, including an ultra-low convection stage. In this case, feature A and feature B are plated with the same bump height, as shown by the large overlap in the bump height distribution. In this example, the ultra-low convection conditions slow down the deposition of feature A relative to feature B such that the deposition rate within feature A and feature B is more uniform (compared to where only high convection is used). Ultra-low convection conditions may slow down the plating rate in both features, and these conditions have a more pronounced effect on wider features, causing the relative deposition rates to be less than the desired relative rate and bump height for differently sized features. to be tuned to achieve This result has not previously been achievable using conventional plating techniques.

The plating results shown in FIGS. 6A and 6B relate to copper electroplating. Although these figures show that ultra-low convection plating methods can be used to achieve a uniform bump height between differently sized features, these same methods can be used in different It is understood that it can be used to target a specific desired height gap between features. This may be achieved by controlling the convection conditions and the time at which the convection conditions are changed. In such cases, it may be desirable to ensure that feature B is longer than feature A by a specified height gap at the end of copper electroplating. A tin or tin-silver cap layer may then be deposited on the copper layer, which is then reflowed after the photoresist is removed. Because differently sized features will reflow the cap layer to different degrees, the targeted gap height can ensure that the features are the same height after the cap layer is reflowed.

Device

The methods described herein may be performed by any suitable device. A suitable apparatus includes a system controller having instructions for controlling hardware and process operations to achieve process operations according to the present embodiments. For example, in some embodiments, hardware may include one or more process stations included in a process tool.

7 presents an example of an electroplating cell in which electroplating may occur. Often, an electroplating apparatus includes one or more electroplating cells in which substrates (eg, wafers) are processed. For the sake of clarity, only one electroplating cell is shown in FIG. 7 . To optimize bottom-up electroplating, additives (eg accelerators, inhibitors and levelers) are added to the electrolyte; Electrolytes with additives may react with the anode in undesirable ways. Therefore, the anode region and the cathode region of the plating cell are sometimes separated by a membrane so that plating solutions of different compositions may be used in each region. The plating solution in the cathode solution is referred to as catholyte, and the plating solution in the anode region is referred to as anolyte. A number of engineering designs can be used to introduce anolyte and catholyte into the plating apparatus.

Referring to FIG. 7 , an illustrative cross-sectional view of an electroplating apparatus 701 according to one embodiment is shown. A plating bath 703 contains a plating solution (having a composition as provided herein), shown as level 705 . The catholyte portion of the vessel is configured to receive a substrate within the catholyte. A wafer 707 is immersed in the plating solution and is held by, for example, a "clamshell" substrate holder 709 mounted on a rotatable spindle 711, which rotatably holds the wafer 707 together with the clamshell substrate. Allows rotation of the holder 709. A general description of a clamshell type plating apparatus having aspects suitable for use in the present invention is described in U.S. Patent No. 6,156,167 to Patton et al. and U.S. Patent No. 6,800,187 to Reid et al., which are incorporated herein in their entirety. is cited as a reference.

An anode 713 is disposed below the wafer within the plating bath 703 and is separated from the wafer area by a membrane 715, preferably an ion selective membrane. For example, Nafion ^™ cation exchange membrane (CEM) can be used. The area below the anodic membrane is sometimes referred to as the “anode chamber”. The ion-selective anode membrane 715 allows ions to communicate between the anode and cathode regions of the plating cell and at the same time prevents particles generated at the anode from moving near the wafer and contaminating the wafer. Anode membranes are also useful for improving plating uniformity by redistributing current flow during the plating process. Details of suitable anodic membranes are provided in US Pat. Nos. 6,126,798 and 6,569,299 to Reid et al., both of which are incorporated herein by reference in their entirety. Ion exchange membranes, such as cation exchange membranes, are particularly suitable for these applications. Such membranes are typically made of ionomeric materials, for example perfluorinated co-polymers containing sulfonic groups (eg Nafion ^™ ), sulfonated polyimides ( sulfonated polyimides), and other materials known to those skilled in the art to be suitable for cation exchange. Selected examples of suitable Nafion ^™ membranes include the N324 membrane and the N424 membrane available from Dupont de Nemours Co.

During plating, ions from the plating solution are deposited on the substrate. Metal ions must diffuse through the diffusion boundary layer and into the TSV hole or other feature. A typical way to assist this diffusion is through convective flow of the electroplating solution provided by pump 717. Additionally, a vibratory agitation or sonic agitation member may be used in conjunction with wafer rotation. For example, a vibration transducer 708 can be attached to the clamshell substrate holder 709 .

A plating solution is continuously provided to the plating bath 703 by a pump 717 . In general, the plating solution flows upward through the anode membrane 715 and diffuser plate 719 to the center of the wafer 707 and then radially outward across the wafer 707 . Also, the plating solution may be provided from one side of the plating bath 703 to the anode region of the plating bath. Then, the plating solution overflows the plating bath 703 into the overflow reservoir 721 . The plating solution is then filtered (not shown) and returned to pump 717 to complete recirculation of the plating solution. In certain configurations of the plating cell, a separate electrolyte is circulated through the portion of the plating cell in which the anode is housed, while mixing with the main plating solution is prevented using sparingly permeable membranes or ion selective membranes.

The reference electrode 731 is located outside the plating bath 703 in a separate chamber 733, which chamber is filled with a solution overflowed from the main plating bath 703. Alternatively, in some embodiments, the reference electrode is positioned as close to the substrate surface as possible and the reference electrode chamber is connected to the side of the wafer substrate or directly underneath the wafer substrate via a capillary tube or other method. In some of the preferred embodiments, the device further includes contact sense leads connected to the wafer periphery and configured to sense the potential of the metal seed layer at the periphery of the wafer, but do not pass any current to the wafer.

A reference electrode 731 is typically employed where electroplating is required to be performed at a controlled potential. Reference electrode 731 may be one of a variety of commonly used types such as mercury/mercury sulfate, silver chloride, saturated calomel or copper metal. A contact sense lead (not shown) in direct contact with the wafer 707 may be used in some embodiments for more accurate potential measurement in conjunction with a reference electrode.

A DC power supply 735 can be used to control current flow to wafer 707 . DC power supply 735 has a negative output lead 739 electrically connected to wafer 707 through one or more slip rings, brushes, and contacts (not shown). A positive output lead 741 of the power supply 735 is electrically connected to an anode 713 located in the plating bath 703. The power supply 735, reference electrode 731 and contact sense leads (not shown) are connected to a system controller 747 which, among other functions, regulates the current and potential provided to the elements of the electroplating cell. make it possible For example, the controller may cause electroplating to be in a regime where the potential is controlled and the current is controlled. The controller contains program instructions that specify the current and voltage levels that need to be applied to the various elements of the plating cell and the times at which these levels must change. When forward current is applied, the power supply 735 biases the wafer 707 so that it has a negative potential with respect to the anode 713 . Thereby, current flows from the anode 713 to the wafer 707 and electrochemical reduction (eg, Cu ^{2 +} + 2 e ^- = Cu ⁰ ) occurs on the wafer surface (cathode), so that electrical A layer (e.g., copper) that is electrically conductive is deposited. An inert anode 714 may be installed below the wafer 707 in the plating bath 703 and may be separated from the wafer area by a membrane 715 .

The apparatus may further include a heater 745 to maintain the plating solution temperature at a specific level. The plating solution may also be used to transfer heat to other elements of the plating bath. For example, once a wafer 707 is loaded into the plating bath, a heater 745 and pump 717 are used to circulate the plating solution through the electroplating apparatus 701 until the temperature throughout the apparatus is substantially constant. ) may be turned on. In some embodiments, the heater is connected to system controller 747. A system controller 747 may be coupled to the thermocouple to receive feedback of the plating solution temperature within the electroplating apparatus to determine if additional heating is required.

A controller may typically include one or more memory devices, one or more mass storage devices, and one or more processors. A processor may include a CPU or computer, analog input/output connections and/or digital input/output connections, stepper motor control boards, and the like. In certain embodiments, the controller controls all activities of the electroplating apparatus. A non-transitory machine-readable medium containing instructions for controlling process operations according to the present embodiments may be coupled to the system controller.

Typically there will be a user interface associated with controller 747. The user interface may include user input devices such as display screens, graphical software displays of apparatus and/or process conditions, pointing devices, keyboards, touch screens, microphones, and the like. Computer program code for controlling the electroplating processes may be written in any conventional computer readable programming language: eg, assembly language, C, C++, Pascal, Fortran, or others. The compiled object code or script is executed by the processor to perform the tasks identified within the program. One example of a plating apparatus that may be used in accordance with embodiments herein is a Lam Research Saber tool. Electrodeposition can be performed on the components forming a larger electrodeposition device.

8 shows a simplified cross-sectional view of an electroplating apparatus according to certain embodiments. The apparatus includes an electroplating cell 801, with a substrate 802 positioned in a substrate holder 803. The substrate holder 803 is often referred to as a cup and may support a substrate 802 on its periphery. An anode 804 is located near the bottom of the electroplating cell 801 . The anode 804 is separated from the substrate 802 by a membrane 805, supported by a membrane frame 806. Because the membrane frame 806 defines the upper end of the anode chamber housing the anode, it is sometimes referred to as the anode chamber membrane frame. Also, the anode 804 is separated from the substrate 802 by an ionic resistive element 807. The ionically resistive element 807 includes openings, which allow electrolyte to travel through the ionically resistive element 807 to impinge on the substrate 802 . A front side insert 808 is positioned over the ionically resistive element 807, proximate to the periphery of the substrate 802. The front side insert 808 may be ring-shaped, as shown, or may be azimuthally non-uniform. The front side insert 808 is sometimes also referred to as a cross flow confinement ring.

Below the membrane 805 is an anode chamber 812 , in which the anode 804 is located. An ionic resistive element manifold 811 is above the membrane 805 and below the ionic resistive element 807 . An irrigation flute 816 may serve to deliver catholyte to the ionically resistive element manifold 811 and to irrigate the membrane 805 during electroplating. In this example, irrigation flutes 816 are fed with electrolyte passing through catholyte inlet 818 . A cross flow manifold 810 is above the ionic resistive element 807 and below the substrate 802 . The height of the cross flow manifold is considered the distance between the substrate 802 and the plane of the ionically resistive element 807 (excluding the ribs 815 on the top surface of the ionically resistive element 807, if present). In some cases, the cross flow manifold may have a height of about 1 mm to 4 mm, or about 0.5 mm to 15 mm in height. The cross flow manifold 810 is defined on the sides by front side inserts 808 and serves to contain the cross flow electrolyte within the cross flow manifold 810 . Side inlet 813 to cross flow manifold 810 is azimuthally opposed to side outlet 814 to cross flow manifold 810 . Side inlet 813 and side outlet 814 may be formed at least in part by front side insert 808 . As shown by the arrows in FIG. 8 , electrolyte travels from the catholyte inlet 818 , through the side inlet 813 , into the cross flow manifold 810 , and out the side outlet 814 . In addition, electrolyte may be introduced into the ionically resistive element manifold 811 via one or more inlets (eg, inlets of the irrigation flute 816 and/or other inlets) into the ionically resistive element manifold 811 . , may travel through the openings of the ionic resistive element 807, into the cross flow manifold 810, and out of the side outlet 814. After passing through the side outlet 814, the electrolyte overflows over the weir wall 809. The electrolyte may be recovered and recycled.

In certain embodiments, the ionic resistive element 807 is close to a near constant and uniform current source close to the substrate (cathode), and as such, in some contexts, a high resistance virtual anode (HRVA) or a channeled ionically resistive element (CIRP). ) may also be referred to as Usually, the ionically resistive element 807 is placed very close to the wafer. Conversely, an anode that is equally fairly close to the substrate is much less suitable for supplying nearly the same current to the wafer, but hardly supports a constant potential plane on the anode metal surface, allowing the current to be the largest and extending from the anode plane to the endpoint ( For example, with peripheral contact points on the wafer) the net resistance is smaller. Thus, although ionic resistive element 807 is referred to as HRVA, this does not imply that the two are electrochemically interchangeable. Under certain operating conditions, the ionic resistive element 807 is better described as a fairly proximate, perhaps hypothetical, uniform current source that is supplied with an almost constant current across the top surface of the ionic resistive element 807 .

The ionic resistive element 807, in many, but not all, implementations, includes micro-sized (typically less than 0.04") through-holes that are spatially and ionically isolated from each other and do not form interconnection channels within the body of the ionic resistive element. These through-holes are sometimes referred to as non-communicating through-holes They typically extend in one dimension and are often, but not necessarily, orthogonal to the plated surface of the wafer (in some embodiments, the holes are ion-resistant oblique with respect to the wafer, generally parallel to the element front surface). Usually through holes are parallel to each other. Usually through holes are arranged in a rectangular array. Sometimes, the layout is an offset spiral pattern. These through holes are Since the holes reconstruct both ionic current flow and (in certain cases) fluid flow internally parallel to the surface and straighten the path of both current and fluid flow toward the wafer surface, the channels extend in three dimensions and form an interconnecting pore. Distinguished from the 3-D porous networks, forming structures However, in certain embodiments, such a porous plate having an interconnected network of pores may also be used as an ion-resistant element Wafer from the top surface of the plate When the distance to is small (e.g., a gap of about 1/10 the size of the wafer radius, e.g., less than about 5 mm), the divergence of both the current flow and the fluid flow occurs in the ionically resistive element channels. Locally limited to, forwarding (impart), and sorted.

One exemplary ionically resistive element 807 is a disk made of a rigid, non-porous dielectric material that is both ionically and electrically resistive. The material is also chemically stable in the plating solution used. In certain cases the ionically resistive element 807 is a ceramic material having about 6,000 to 12,000 non-communicating through holes (eg, aluminum oxide, stannic oxide, titanium oxide, or mixtures of metal oxides) or It is made of a plastic material (eg, polyethylene, polypropylene, PVDF (polyvinylidene difluoride), polytetrafluoroethylene, polysulfone, PVC (polyvinyl chloride), polycarbonate, etc.). In many embodiments, the ionic resistive element 807 has substantially the same width as the wafer (eg, the ion resistive element 807 has a diameter of about 300 mm when used with a 300 mm wafer) and the wafer , eg directly under the wafer in a wafer-down-facing electroplating apparatus. Preferably, the plated surface of the wafer is within about 10 mm, more preferably within about 5 mm, of the surface of the nearest ionically resistant element. Accordingly, the top surface of the ionically resistive element 807 may be flat or substantially flat. Often, both the top and bottom surfaces of the ionically resistive element 807 are flat or substantially flat. However, in many embodiments, the top surface of the ionically resistive element 807 includes a series of linear ribs, as described further below.

As above, the overall ionic resistance and flow resistance of the plate 807 is dependent on both the thickness and overall porosity (fraction of area available for flow through the plate) and the size/diameter of the holes. Plates of lower porosity will have higher impingement flow velocities and ionic resistances. Comparing plates of the same porosity with smaller diameter 1-D holes (and therefore a larger number of 1-D holes), more discrete current sources, which function more as key sources that can diffuse across a small gap, Because it is present, it will have a more finely-uniform distribution of current on the wafer, and will also have a higher total pressure drop (higher viscosity flow resistance).

In some cases, about 1-10% of the ionic resistive element 807 is an open area through which ionic current can pass (and electrolyte can pass through, if there is no other element blocking the openings) am. In certain embodiments, about 2-5% of the ionic resistive element 807 is open area. In a specific example, the open area of the ionic resistive element 807 is about 3.2% and the effective total open cross-sectional area is about 23 cm 2 . In some embodiments, the non-communicating holes formed in the ionic resistive element 807 have a diameter of about 0.01 to 0.08 inches. In some cases, the holes have a diameter of about 0.02 to 0.03 inches, or about 0.03 to 0.06 inches. In various embodiments the holes have a diameter that is at most about 0.2 times the gap distance between the ionically resistive element 807 and the wafer. The holes need not be, but are generally circular in cross section. Also, to facilitate construction, all holes of the ionically resistive element 807 may have the same diameter. However, this need not be the case, and both the individual size and local density of the holes may vary across the surface of the ionically resistive element as specific requirements may dictate.

The ionically resistive element 807 shown in FIG. 8 includes a series of linear ribs 815 extending into and out of the page. Ribs 815 are sometimes referred to as projections. The ribs 815 are located on the top surface of the ionically resistive element 807 and in many cases are oriented such that their length (eg, their longest dimension) is perpendicular to the direction of the cross flow electrolyte. In certain embodiments, ribs 815 may be oriented such that their length is parallel to the direction of the cross flow electrolyte. Ribs 815 affect fluid flow and current distribution within cross flow manifold 810 . For example, the cross flow of electrolyte is generally confined to the area above the top surface of ribs 815, creating a high rate of electrolyte cross flow. In the regions between adjacent ribs 815, the current passed upwardly through the ionic resistive element 807 is redistributed, making it more uniform before passing to the substrate surface.

8, the direction of the cross flow electrolyte is from left to right (e.g., from side inlet 813 to side outlet 814), and ribs 815 are oriented such that lengths extend in and out of the page. In certain embodiments, ribs 815 may have a width of between about 0.5 mm and 1.5 mm or between about 0.25 mm and 10 mm (measured from left to right in FIG. 8 ). The ribs 815 may have a height of about 1.5 mm to 3.0 mm or about 0.25 mm to 7.0 mm (measured from top to bottom in FIG. 8 ). Ribs 815 may have a height to width aspect ratio (height/width) of about 5/1 to 2/1 or about 7/1 to 1/7. The ribs 815 may have a pitch of about 10 mm to 30 mm or about 5 mm to 150 mm. The ribs 815 may have variable lengths (measured in and out of the page in FIG. 8 ) extending across the face of the ionically resistive element 807 . The distance between the top surface of the ribs 815 and the surface of the substrate 802 may be between about 1 mm and 4 mm, or between about 0.5 mm and 15 mm. Ribs 815 may be provided over a region, having approximately the same area as the substrate, as shown in FIG. 8 . The channels/openings of the ionic resistive element 807 may be located between adjacent ribs 815, or may extend through the ribs 815 (in other words, the ribs 815 may be channeled may or may not be channeled). In some other embodiments, the ionic resistive element 807 may have a flat (eg, not including ribs 815) top surface. The electroplating apparatus shown in FIG. 8, which includes an ionic resistive element with ribs thereon, is disclosed in U.S. Patent No. “ENHANCEMENT OF ELECTROLYTE HYDRODYNAMICS FOR EFFICIENT MASS TRANSFER DURING ELECTROPLATING,” which is incorporated herein by reference in its entirety. 9,523,155 for further discussion.

The device may also contain various additional elements needed for a particular application. In some cases, an edge flow element may be provided proximate to the periphery of the substrate within the cross flow manifold. An edge flow element may be shaped and positioned to promote a high degree of electrolyte flow (eg, cross flow) near the edges of the substrate. The edge flow element may be ring-shaped or arc-shaped in certain embodiments, and may be azimuthally uniform or non-uniform. Edge flow elements are further discussed in U.S. Patent Application Serial No. 14/924,124, entitled "EDGE FLOW ELEMENT FOR ELECTROPLATING APPARATUS," filed on October 27, 2015, which is incorporated herein by reference in its entirety.

In some cases, the device may include a sealing member to temporarily seal the cross flow manifold. The sealing member may be ring-shaped or arc-shaped, and may be positioned proximate the edges of the cross flow manifold. While a ring-shaped sealing member may seal the entire cross-flow manifold, an arc-shaped sealing member may seal a portion of the cross-flow manifold (leaving the side outlet open in some cases). During electroplating, the sealing member may be repeatedly engaged and disengaged to seal and unseal the cross flow manifold. The sealing member may be engaged and disengaged by moving the substrate holder, ionically resistive element, front side insert, or other part of the device that engages the sealing member. Sealing members and methods of controlling cross flow are disclosed in the following U.S. Patent Applications: filed August 1, 2016, entitled "DYNAMIC MODULATION OF CROSS FLOW MANIFOLD DURING ELECTROPLATING, each of which is hereby incorporated by reference in its entirety. "U.S. Patent Application Serial No. 15/225,716; and US Patent Application Serial No. 15/161,081, filed May 20, 2016, entitled "DYNAMIC MODULATION OF CROSS FLOW MANIFOLD DURING ELECTROPLATING".

In various embodiments, one or more electrolyte jets may be provided to provide additional electrolyte onto the ionic resistive element. Electrolyte flushing may deliver electrolyte closer to the periphery of the substrate, or to a location closer to the center of the substrate, or both. The electrolyte jet may be directed at any location and may deliver a cross flow electrolyte, a collision electrolyte, or a combination thereof. Electrolytic bursts are further discussed in U.S. Patent Application Serial No. 15/455,011, entitled "ELECTROPLATING APPARATUS AND METHODS UTILIZING INDEPENDENT CONTROL OF IMPINGING ELECTROLYTE," filed March 9, 2017, which is incorporated herein by reference in its entirety. do.

9 is a schematic diagram of a top view of an exemplary electrodeposition apparatus. Electroplating apparatus 900 can include three separate electroplating modules 902 , 904 , and 906 . Electrodeposition apparatus 900 can also include three separate modules 912, 914, and 916 configured for various process operations. For example, in some embodiments, one or more modules 912, 914, and 916 may be spin rinse drying (SRD) modules. In other embodiments, one or more modules 912, 914, and 916 may be post-electrofill modules (PEMs), each processed by one of electroplating modules 902, 904, and 906. Afterwards, it is configured to perform functions such as edge bevel removal of substrates, backside etching and acid cleaning.

Electrodeposition apparatus 900 includes a central electrodeposition chamber 924 . The central electrodeposition chamber 924 is a chamber that holds the chemical solution used as the electroplating solution in the electroplating modules 902 , 904 , and 906 . The electrodeposition apparatus 900 also includes a dosing system 926 that may store and deliver additives to the electroplating solution. A chemical dilution module 922 may store and mix chemicals to be used as etchants. A filter and pumping unit 928 may filter the electroplating solution to the central electrodeposition chamber 924 and may pump it to the electroplating modules.

System controller 930 provides the electronic and interface controls required to operate electrodeposition apparatus 900 . A system controller 930 (which may include one or more physical or logical controllers) controls some or all of the attributes of the electroplating apparatus 900 .

Signals for monitoring the process may be provided by analog and/or digital input connections of system controller 930 from various process tool sensors. Signals to control the process may be output to analog and digital output connections of the process tool. Non-limiting examples of process tool sensors that may be monitored include mass flow controllers, pressure sensors (eg manometers), thermocouples, optical position sensors, and the like. Appropriately programmed feedback and control algorithms may use data from these sensors to maintain process conditions.

Hand-off tool 940 may select a substrate from a substrate cassette such as cassette 942 or cassette 944 . Cassettes 942 or 944 may be front opening unified pods (FOUPs). A FOUP is an enclosure designed to stably and safely hold substrates in a controlled atmosphere and allow substrates to be removed for processing or measurement by tools equipped with appropriate load ports and robotic handling systems. Hand-off tool 940 may hold the substrate using vacuum attachment or some other attachment mechanism.

The hand-off tool 940 may interface with a wafer handling station 932 , cassettes 942 or 944 , a transfer station 950 , or an aligner 948 . From the transfer station 950, a hand-off tool 946 may gain access to the substrate. Transfer station 950 may be a slot or location that may transfer substrates to and from hand-off tools 940 and 946 without passing through aligner 948 to hand-off tools 940 and 946 . However, in some embodiments, to ensure that the substrate is properly aligned on the hand-off tool 946 for precision transfer to the electroplating module, the hand-off tool 946 is coupled with the aligner 948 and the substrate. can also be sorted. The hand-off tool 946 may also transfer a substrate to one of the electroplating modules 902, 904, or 906 configured for various process operations or to one of three separate modules 912, 914, and 916. there is.

An example of a process operation according to the methods described above is: (1) electrodepositing copper or another material onto a substrate in electroplating module 904 and (2) rinsing and drying the substrate in an SRD in module 912 and (3) performing edge bevel removal in module 914.

An apparatus configured to enable effective cycling of substrates through sequential plating, rinsing, drying and PEM process operations may be useful in implementations for use in a manufacturing environment. To accomplish this, module 912 can be configured as a spin rinse dryer and edge bevel removal chamber. Using this module 912, the substrate only has to be transferred between the electroplating module 904 and the module 912 for copper plating and EBR operations. In some embodiments, the methods described herein will be implemented in a system that includes an electroplating apparatus and a stepper.

system controller

In some implementations, the controller is part of a system, which may be part of the examples described above. Such systems can include semiconductor processing equipment, including a processing tool or tools, a chamber or chambers, a platform or platforms for processing, and/or certain processing components (wafer pedestal, gas flow system, etc.) . These systems may be integrated with electronics for controlling their operation before, during and after processing of a semiconductor wafer or substrate. Electronics may be referred to as a “controller” that may control various components or subparts of a system or systems. The controller controls the delivery of processing gases, temperature settings (eg, heating and/or cooling), pressure settings, vacuum settings, power settings, depending on processing requirements and/or type of system. , radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid transfer settings, position and motion settings, tools and other transfer tools, and/or It may be programmed to control any of the processes disclosed herein, including transfers of wafers into and out of loadlocks coupled to or interfaced with a particular system.

Generally speaking, a controller receives instructions, issues instructions, controls operations, enables cleaning operations, enables endpoint measurements, and/or various integrated circuits, logic, memory, and/or It can also be defined as an electronic device with software. Integrated circuits are chips in the form of firmware that store program instructions, chips defined as digital signal processors (DSPs), application specific integrated circuits (ASICs) and/or one that executes program instructions (eg, software). It may include the above microprocessors or microcontrollers. Program instructions may be instructions passed to a controller or system in the form of various individual settings (or program files) that specify operating parameters for executing a specific process on or on a semiconductor wafer. In some embodiments, operating parameters are set to achieve one or more processing steps during fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and/or dies of a wafer. It may be part of a recipe prescribed by engineers.

A controller may be part of or coupled to a computer, which in some implementations may be integrated into, coupled to, or otherwise networked to the system, or a combination thereof. For example, the controller may be all or part of a fab host computer system that may enable remote access of wafer processing or may be in the "cloud." The computer monitors the current progress of manufacturing operations, examines the history of past manufacturing operations, examines trends or performance metrics from multiple manufacturing operations, changes parameters of current processing, and executes processing steps following current processing. You can also enable remote access to the system to set up, or start new processes. In some examples, a remote computer (eg, server) can provide process recipes to the system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and/or settings that are then transferred from the remote computer to the system. In some examples, the controller receives instructions in the form of data that specify parameters for each of the process steps to be performed during one or more operations. It should be understood that these parameters may be specific to the type of tool the controller is configured to control or interface with and the type of process to be performed. Thus, as described above, a controller may be distributed, for example by including one or more separate controllers that are networked together and cooperate together for a common purpose, for example, for the processes and controls described herein. An example of a distributed controller for these purposes is one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (e.g., at platform level or as part of a remote computer) that are combined to control a process on the chamber. can be circuits.

Exemplary systems, without limitation, include plasma etch chambers or modules, deposition chambers or modules, spin-rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, bevel edge etch chambers or modules, physical vapor deposition (PVD) chamber or module, chemical vapor deposition (CVD) chamber or module, atomic layer deposition (ALD) chamber or module, atomic layer etch (ALE) chamber or module, ion implantation chamber or module, track chamber or module, and semiconductor and any other semiconductor processing systems that may be used in or associated with the fabrication and/or fabrication of wafers.

As described above, depending on the process step or steps to be performed by the tool, the controller is used in material transfer to move containers of wafers to and from tool locations and/or load ports in a semiconductor fabrication plant. may communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, neighboring tools, neighboring tools, tools located throughout the plant, the main computer, another controller or tools. .

The various hardware and method embodiments described above may be used in conjunction with lithographic patterning tools or processes for the fabrication or fabrication of, for example, semiconductor devices, displays, LEDs, photovoltaic panels, and the like. Typically, though not necessarily, these tools/processes will be performed and used together in a common manufacturing facility.

Lithographic patterning of a film is typically performed in the following steps, each of which is enabled using a number of possible tools: (1) a workpiece using either a spin-on tool or a spray-on tool. , for example, applying a photoresist onto a substrate having a silicon nitride film formed thereon; (2) curing the photoresist using a hot plate or furnace or other suitable curing tool; (3) exposing the photoresist to visible or UV or x-ray light using a tool such as a wafer stepper; (4) developing the resist to selectively remove the resist using a tool such as a wet bench or spray developer to pattern the resist; (5) transferring the resist pattern into an underlying film or workpiece by using a dry or plasma assisted etching tool; and (6) removing some or all of the resist using a tool such as an RF or microwave plasma resist stripper. In some embodiments, an ashesable hard mask layer (eg an amorphous carbon layer) and another suitable hard mask (eg an antireflective layer) may be deposited prior to applying the photoresist.

It is understood that the configurations and/or approaches described herein are illustrative in nature and that these specific embodiments or examples are not to be regarded in a limiting sense as many variations are possible. Certain routines or methods described herein may represent one or more of any number of processing strategies. As such, the various functions illustrated may be performed in the order illustrated, in other orders, concurrently, or in some cases omitted. Similarly, the order of the processes described above may be varied. Certain references are incorporated herein by reference. It is understood that any disclaimers or denials made in these references do not necessarily apply to the embodiments described herein. Similarly, any features described as essential in these references may be omitted from embodiments herein.

Subject matter of this disclosure is subject to all novel and nonobvious disclosures of various processes, systems, and configurations, and other features, acts, functions, and/or attributes disclosed herein, as well as any and all equivalents thereof. Includes combinations and subcombinations.

Claims (19)

A method of electroplating a material on a substrate, comprising:
providing a substrate to an electroplating apparatus, the substrate being a semiconductor substrate comprising a plurality of features recessed into a surface of the substrate;
immersing the substrate in the electrolyte of the electroplating apparatus;
in a first stage, electroplating a material onto the substrate while flowing an electrolyte in or through the electroplating apparatus to provide a medium convection condition or a high convection condition to the surface of the substrate;
switching from the first stage to the second stage when a first switching condition is satisfied;
In the second stage, electroplating the material onto the substrate while flowing electrolyte in or through the electroplating apparatus to provide ultra-low convection conditions to the surface of the substrate. doing; and
removing the substrate from the electrolyte;
in the ultra-low convection conditions, electrolyte flow proximate the surface of the substrate is laminar, and mass transport of metal ions of the electrolyte within the features is predominantly diffusional rather than convective over at least 75% of the depth of the features; , and
wherein the medium convection condition or the high convection condition provides greater convection to the surface of the substrate compared to the ultra-low convection conditions. According to claim 1,
The high convection conditions are applied during the first stage, wherein (i) the electrolyte flow proximate the surface of the substrate is turbulent, and/or (ii) the surface of the substrate wherein a rate of electrolyte flow approaching is one of within 10% of the rate at which turbulence is achieved. According to claim 1,
wherein the intermediate convection conditions are applied during the first stage, wherein mass transport of metal ions of the electrolyte in the features at the intermediate convection conditions predominates in diffusion rather than convection over 50% or less of the depth of the features. electroplating method. According to any one of claims 1 to 3,
wherein the first switching condition is satisfied when the electrolyte sufficiently diffuses into the features. According to any one of claims 1 to 3,
wherein the first switching condition is satisfied when the current applied to the substrate is less than or equal to the limiting current to be experienced when switching to the second stage. According to any one of claims 1 to 3,
The electroplating method of claim 1 , wherein the first switching condition is satisfied when organic plating additives including at least an inhibitor are stabilized in the features. According to any one of claims 1 to 3,
The first switching condition is,
(a) the electrolyte is sufficiently diffused into the features;
(b) the current applied to the substrate is less than or equal to the limiting current to be experienced when switching to the second stage; and
(c) the electroplating method is satisfied when organic plating additives, including at least an inhibitor, are stabilized within the features. According to any one of claims 1 to 3,
switching from the second stage to a third stage when a second switching condition is satisfied; and
In the third stage, electroplating the material onto the substrate while flowing an electrolyte in or through the electroplating apparatus to provide the medium convection condition or the high convection condition to the surface of the substrate. Electroplating method further comprising the step of doing. According to claim 8,
The features include a first feature and a second feature, the first feature having a wider CD compared to the second feature, each of the first feature and the second feature measured from a common reference plane. and wherein the second switching condition is satisfied when a difference between the instantaneous height of the second feature and the instantaneous height of the first feature reaches a target height gap. According to claim 9,
wherein the target height gap is at least 0.5 μm. According to claim 10,
wherein the target height gap is at least 1 μm. According to claim 10,
wherein the CD of the first feature is at least 20 μm wider than the second feature, and the target height gap is at least 2 μm. According to claim 8,
wherein the second switching condition considers a target that is within wafer non-uniformity with respect to the substrate. According to any one of claims 1 to 3,
wherein the features include a first feature and a second feature, the first feature having a wider CD compared to the second feature. 15. The method of claim 14,
the features are defined in the photoresist layer;
The method,
after removing the substrate from the electrolyte, forming a cap layer on the material deposited in the features;
after forming the cap layer, removing the photoresist from the surface of the substrate; and
and reflowing the cap layer. According to claim 15,
After the cap layer is reflowed, a height gap between the first feature and the second feature is less than before the cap layer is reflowed, the height gap being the instantaneous height of the first feature as measured from a common reference plane. and the instantaneous height of the second feature. According to claim 15,
The height gap between the first feature and the second feature before the cap layer is reflowed is at least 2 μm, and after the cap layer is reflowed, the height gap between the first feature and the second feature is wherein the height gap is 0.5 μm or less. 18. The method of claim 17,
and after the cap layer is reflowed, the height gap between the first feature and the second feature is 0.1 μm or less. An apparatus for electroplating a material onto a substrate, comprising:
electroplating chamber;
substrate support; and
As a controller,
causing a substrate to be provided to an electroplating apparatus, wherein the substrate is a semiconductor substrate including a plurality of features recessed into a surface of the substrate;
causing the substrate to be immersed in the electrolyte in the electroplating apparatus;
in a first stage, causing the material to be electroplated onto the substrate while flowing an electrolyte into or through the electroplating apparatus to provide a medium convection condition or a high convection condition to the surface of the substrate;
switch from the first stage to a second stage when a first switching condition is satisfied;
in the second stage, causing the material to be electroplated onto the substrate while flowing an electrolyte in or through the electroplating apparatus to provide ultra-low convection conditions to the surface of the substrate;
configured to cause the substrate to be removed from the electrolyte;
in the ultra-low convection conditions, electrolyte flow adjacent the surface of the substrate is laminar, and mass transport of metal ions of the electrolyte within the features is predominantly diffusional rather than convective over at least 75% of the depth of the features; , and
wherein the medium convection condition or the high convection condition provides greater convection to the surface of the substrate compared to the ultra-low convection conditions.

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